The present invention relates to a flexible joint with two sealing lines of different perimeters, whereof one is inscribed in the other. It more specifically, but not exclusively, relates to a joint with a non-circular shape having curvilinear portions.
More precisely the invention relates to a joint having two sealing lines constituted by two closed elementary joints of different length and whose axes are located in the same plane. Such a joint provides a double seal between an inner chamber and an outer chamber or a seal of the same quality between an intermediate chamber defined between the joints and the inner and outer chambers, whilst offering the possibility of checking the seal provided by each of the elementary joints.
More specifically the present invention relates to a joint with two sealing lines constituted by two elementary joints of the type having an inner spring with contiguous turns closed on itself and at least one outer metal casing in which is fitted the said spring. A metal joint of this type is described and claimed in French Pat. No. 2 151 186 in the name of the Commisariat a l'Energie Atomique. Compared with conventional elastic joints such as elastomer joints, this type of joint has the essential advantage of being compatible with all media and in particular corrosive or radioactive media.
Flexible joints with two sealing lines and in particular having an annular shape are known, which make it possible to ensure a double seal, whilst permitting an inspection to be made of said seal. However, all the known joints comprise at least one elastic, particularly elastomer, unitary joint positioned outside the metal joint. It has hitherto been impossible, due to the absence of elasticity in the metal joints, to provide such a joint on the outer periphery of a joint having two sealing lines, particularly when said joint has a non-circular shape.